August 23, 2007
Scientists Study Out-Of-Body Experiences
WASHINGTON -- The stories seem strange but riveting. A heart attack victim recalls floating in the air, watching paramedics revive him. A surgical patient remembers hovering, watching the doctors operate. Such widely reported out-of-body experiences have long been the territory of theology, philosophy and scary movies. Now scientists have turned their attention to the topic.
Researchers in England and Switzerland have figured out ways to confuse the sensory signals received by the brain, allowing people to seem to be standing aside and watching themselves.
The research is described in Friday's edition of the journal Science.
Dr. Henrik Ehrsson of University College London's Institute of Neurology and the Karolinska Institute in Stockholm, explained that he was interested in a person's perception of the "self."
"I'm interested in the question of why I feel that my self is located inside my physical body. How does my brain know that I am standing right here," he said.
And what would happen to the self if a person could effectively move their eyes to another part of the room and observe themselves from an outside perspective? Would the self move with the eyes, or stay in the body, he wondered.
So seated volunteers were fitted with head-mounted video displays that allowed them to view themselves from behind, using a pair of video cameras, one for each eye.
A researcher would stand behind them and extend a plastic rod which they could see toward the area just below the cameras. At the same time another plastic rod, which they could not see, touched their chest.
The volunteers said they experienced the feeling of being behind their own body watching. Many found it "weird" and seemingly real, though not scary.
They felt "that their center of awareness 'self' is located outside their physical bodies and that they look at their bodies from the perspective of another person," he reported.
"The idea is to change the visual input and its relationship to the tactile information," he said. "The brain is always trying to interpret sensory information. The brain can trick itself."
In a second test, Ehrsson connected sensors to the skin to measure electrical conductance, which indicates emotional response.
He then allowed them to watch a hammer swing down to a point below the camera, as though it were going to hurt an unseen portion of the virtual body.
Their skin conductance registered emotional responses including fear, indicating they sensed their selves had left their physical bodies and moved to the virtual bodies where the hammer was swung.
The research has applications in neuroscience and also potentially in industrial applications involving virtual reality, he said.
Meanwhile, a team led by Olaf Blanke, a professor at the Laboratory of Cognitive Neuroscience at Ecole Polytechnique Federale in Lausanne, Switzerland, conducted a similar experiment using virtual reality goggles.
In these tests, the subjects could see a three-dimensional representation of their body, the body of a dummy, or a simple object directly in front of them. The subject then saw the back of the image being stroked with a paintbrush, either in or out of sync with someone stroking his own back.
Then the participants were blindfolded and backed up, and then asked to return to their original position.
Those whose backs were stroked synchronously with the virtual image of themselves or the human dummy consistently overshot their position in the direction of the image; but subjects who saw no virtual image or a simple object did not.
The study aimed at determining how senses play a role in self consciousness, Blanke said.
Ehrsson's research was funded by the Wellcome Trust, the Presence: Research Encompassing Sensory Enhancement, Neuroscience, Cerebral-Computer Interfaces and Applications Project, the Human Frontier Science Program, Swedish Medical Research Council and the Swedish Foundation for Strategic Research. Blanke's work was funded by the Cojito Foundation, Foundation de Familie Sandoz, the Foundation Odier and the Swiss National Science Foundation.
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